If branch conditions' one successor is dominating another non-latch successor then this loop's iteration space can not be restricted. In this example block bb5 is always executed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@65902 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 15 insertions, 0 deletions

diff --git a/lib/Transforms/Scalar/LoopIndexSplit.cpp b/lib/Transforms/Scalar/LoopIndexSplit.cpp
index 6311e17..e93d448 100644
--- a/lib/Transforms/Scalar/LoopIndexSplit.cpp
+++ b/lib/Transforms/Scalar/LoopIndexSplit.cpp
@@ -532,6 +532,21 @@ bool LoopIndexSplit::updateLoopIterationSpace() {
   BasicBlock *ExitingBlock = ExitCondition->getParent();
   if (!cleanBlock(ExitingBlock)) return false;
 
+  // If the merge point for BR is not loop latch then skip this loop.
+  if (BR->getSuccessor(0) != Latch) {
+    DominanceFrontier::iterator DF0 = DF->find(BR->getSuccessor(0));
+    assert (DF0 != DF->end() && "Unable to find dominance frontier");
+    if (!DF0->second.count(Latch))
+      return false;
+  }
+  
+  if (BR->getSuccessor(1) != Latch) {
+    DominanceFrontier::iterator DF1 = DF->find(BR->getSuccessor(1));
+    assert (DF1 != DF->end() && "Unable to find dominance frontier");
+    if (!DF1->second.count(Latch))
+      return false;
+  }
+    
   // Verify that loop exiting block has only two predecessor, where one pred
   // is split condition block. The other predecessor will become exiting block's
   // dominator after CFG is updated. TODO : Handle CFG's where exiting block has